Should I get a Eurail pass?

The vast majority of Europe is part of the Schengen Zone, you're only allowed three months in the Schengen Zone and then you must leave for a period of time before returning (three months if memory serves correct, but I could easily be wrong). Whether you get a Eurail pass or not also comes down to where you'll be and how often you'll be on the train. For example if you're travelling extensively in Scandinavia a pass would be economical due to the expensive trains, but if you're travelling extensively in Southern Europe where trains tend to be cheap, it might not be worth it. Also there are a lot of budget airlines popping up and you might want to take those for some of the longer trips.